Interference-reducing means for radio receiving apparatus



Patented Dec. 3, 1929 UNITED STATES @tatiana-r PATENT OFFICE RICHARDHOWL'AND RANGER, OF BROOKLYN, NEW YORK, ASSIGNOR TO RADIO COR- PORATIONOF AMERICA, A CORPORATION OF DELAWARE INTERFERENCE-REDUCING MEANS FORRADIO RECEIVING APPARATUS Application led December 18, 1922. Serial No.607,478.

This invention relates to improved means for combining signals receivedfrom the same current in a vacuum tube detector or amplifier vinaccordance with such signals, in such a Way that the tubes will respondonly to signals which have 'a predetermined phase relationship.

It is an object of this invention to provide such means which willdecrease the interfering effects caused by static disturbances and whichwill also reduce the interfering effects caused by the operation ofanother transmitting station on substantially the same wave length asthe station desired. It is a further object of this invention to providemeans for geographically tuning to select one particular transmitting"station from among several transmitting on substantially the same wavelength. It is a further obj ect of this invention to provide such meanswhich shall have a sharper tuning characteristic than the arrangementsnow used for the purpose, and which shall, at the same time, berelatively inexpensive, simple to construct and install and which shallbe reliable and positive in its operation. Still other objects will beapparent from the specification.

My invention is shown by way of example in the accompanying drawing andis eX- plained in the specification with reference to the embodimentillustrated and its underlying principles will best be understood byreference to the specification and drawing but the scope will beparticularly pointed out in the accompanying claims.

Referring to the drawing,

Figure 1 is a diagram showing the relative position of sending,receiving and recording stations.

Figure 2 is adiagrammatic comparison of the addition law of anarrangement old in the art as shown in dotted lines and of my inventionas shown in full lines. l

Figure 3 is a diagram of the circuit embodying my invention and Figure 4is a diagrammatic elevation view of the filament and grid of a vacuumtube according to my invention.

Figure 5 is a plan view of the same.

Referring to Figure l, let.A represent a transmitting station, B and B.two receiving stations connected by wire lines to theJ common indicatingapparatus at C and le't D be a second transmitting station. It is wellknown in the art that as a wave from stat-ion A travels along, as shownin dotted lines, it will first be taken up at station B and later betaken up at B. This difference in time may be very small but it is,nevertheless, sufficient for certain arrangement of the receivingstation with reference to the transmitting station, to produce largedifference in phase at the indicating apparatus C where the signals arecombined. It has been suggested that in order to obtain maximum signalresponse from the desired transmitting station the signals should bebrought into phase with each other and added together and the resultantsignal thereby obtained utilized to actuate the detector. It has furtherbeen suggested that this adjustment of phase may be accomplished by theuse of phase rotators or phase shifting coils in one or both lines.

It has been found that as the signals are brought into phase they addaccording to the law of cosin'es giving a curve such as shown in dottedlines in Fig. 2. It will be seen by an inspection of this curve as wellas by the application of trigonometry that for signals which are out ofjphase by a substantial amount the response may be almost as great as ifthe signals were absolutely in phase. While this arrangement issatisfactory when the signals from the interfering station have arelatively large phase difference it will not prevent interference whenthe phase difference of the signals is. relatively small.

My invention provides means for overcoming this difficulty and achievinga resultant curve such as shown in full lines in Figure 2. It will beseen by comparison of the curves of Figure 2 that by the use ofapparatus having the characteristic shown in full lines, it is possibleto obtain much greater selectivity as regards interfering stations whenthe interfering station is situated relatively close to the desiredtransmitting station so that the phase difference between signals fromthe interfering station is not greatly different from the phasedifference of signals from the desired station.

It has been found in practice that when one of the wires in the grid ofa detector or amplifier tube is cut out the efficiency drops 0H to avery much greater extent than would be expected. For instance, if a gridconsists of 10 parallel sections of wireand one of these sectionsbreaks; vthe drop in eiiiciency is considerably over 10%. I make use ofthis phenomenon to provide that no response will be obtained from theindicating apparatus unless the signals received at the commonindicating device have a desired and predetermined phase relation andthis is done as follows:

Referring to Figure 3, B and B respectively designate two receivingaerials having different characteristics in one or more respects. Forinstance, they may be located at different distances from thetransmitting station, or they may have diEerent directionalcharacteristics or they may have diiferent electrical characteristics,with reference to tuning, damping etc. Each aerial is provided with theusual tuning means such as, variable inductances l and l and variablecondensers 2 and 2. The signals received upon these aerials may beampliied by the use of any suitable means known in the art if desired orthey may be transmitted over the wire lines to the indicating apparatusat C without amplification, depending upon circumstances. The indicatingapparatus provided at C comprises a multiple section grid amplifier tubedesignated as 3. This tube comprises a hot cathode and an anodeaccording to the well known construction but is provided with aplurality of electrically independent grids 4 and 4. I preferablyarrange these grids as diagrammatically shown in Figs. 4 and 5, in sucha way that each horizontal section of the grid is in the form of anellipse enclosing the filament, this section being attached at one endto the conducting post P, which leads to a contact stud (not shown) inthe base of the tube. As shown by Fig. 4 the sections of the grid areconnected alternately to posts P and P, the post P also leading toanother contact stud in the base of the tube. The signals received fromstation B are impressed across the cathode of tube 3 and the grid 4whereas signals from station B are impressed across the cathode of thetube 3 and the grid 4. Connected in the output circuit of this amplifierI provide a coupling coil 5 for the purpose of impressing the combinedsignal from amplier 3 upon a suitable detector 6 provided with anysuitable indicating or recording means, herein shown as telephonereceivers 7 The amplifier tube 3 is operated at such point of itscharacteristic that the combined action of grids 4 and 4 is required torender it operative;

that is to say signals must be in phase on grids 4 and 4 in order toproduce response of the amplifier.

Turning now to the operation of my receiving apparatus, if it is desiredto recelve signals from station A the phase shifting means will be soadjusted as to bring the signals from A into phase with each other at Cas pointed out above. sponds to maximum response of the indicatingapparatus. Let it now be assumed that it is desired to receive signalsfromstation D. Thephase shifting means will be adj usted to bringsignals from this station into phase at C. It will be apparent thatsignals received from station A will no longer be in phase at C andtherefore will not be reproduced in the output circuit of the amplifierand hence will not affect the indicating or recording apparatus.

It will be seen that I have provided means whereby the combined actionof both aerials giving oscillations having predetermined phase relationis required to cause response of the indicating or recording means. Thisproperty is of advantage in preventing response of the indicating meansto static disturbances since it will be apparent that the only staticdisturbance which can be passed through the amplifier 3 is a disturbancewhich has the same phase relationship as that of the signal desired andit will be seen also that this will prevent disturbance due to anysignal or static which is received upon only one antenna.

While I have shown and described tube 3 as an amplifier, it will beapparent that similar results may he obtained by operating this tube asa detector, and that `the number of aerials to be used may be increasedby providing a grid section for each aerial. Still other modificationsand changes may be made as will be apparent to anyone skilled in the artwithout departing from the spirit of my invention.

Having described my invention I declare that what I claim is:

l. In radio signalling apparatus the combination of a plurality ofaerials, a common receiving means for all of said aerials, a multiplegrid vacuum tube forming a common means for receiving oscillationsreceived on said aerials, means for connecting each of said aerials to aseparate grid member of said tube, and means for applying the signalenergy received on said aerials to said various grid members in a likephase relationship.

2. In radio signalling apparatus the combination of a plurality ofaerials spaced apart a considerable fraction of a wave-length, a vacuumtube having a plurality of grid members each connected to a differentaerial, a phase control means for controlling the phase This conditioncorre-- roo relationship of the signal energy received on all of saidaerial members and thereby impressing the said signal energy upon allgrids simultaneously in like phase relationship and indicating meansoperatively associated with the output circuit of said tube.

3. In radio signalling apparatus the combination of a plurality ofaerials, a common amplifying means for said aerials, said amplifyingmeans comprising a vacuum tube having a grid composed of a plurality ofsections, each section of said grid being con-y each section beingconnected to a different aerial, phase control means fory impressingenergy of like phase relationship simultaneously upon each of said gridsections and indicating means connected in the output circuit of saidamplifying and detecting ,af cans.

j. 6. In radio signalling apparatus the combination of a plurality ofaerials spaced apart la fraction of the signal Wave-length and a tcommondetecting and amplifying means jassociated with said aerials, saiddetecting and amplifying means comprising a vacuum t be having multiplegrid members and res onsive only to the combined in-phase signal energyreceived on all of said aerials.

7. In radio signalling apparatus the combination of a plurality ofspaced aerials, a vacuum Vtube detector comprising a plurality of gridseach connected to a dierent aerial means for impressing signal energy oflike phase relationship from each aerial upon said grids, and indicatingmeans operatively associated with the output circuit of said tube.

8. The method of operating a vacuum tube in response to signals receivedon a plurality of aerials spaced apart a considerable fraction of awave-length of the signalssre'- ceived which comprises subjecting thespace current of the tube simultaneously to the control of signallpotential from eachaerial independently.

9. The method of reducing interference in the reception of radio signalswhich comprises receiving the signal on two aerials separated by aconsiderable distance, and controlling the space current 4of a vacuumtube Vsimultaneously and independently by l the signal potential fromeach aerial.

RICHARD HOWLAND RANGER.

dil

mem No. 1,738,392. Granted December's, 1929, to

RICHARD HowLAND RANGER.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3,line 18, claim 4, after the word ','aerial" insert tlIe words "phasecontrol means for impressing energy of like phase relationshipsimultaneously upon each of said grid sectious,"; same page, lines 28 to30, claim S, strike out the words "phase control means for impressingenergy of like phase relationship simultaneouslyupon each of said gridseetions"; and that the said Letters Patent should be read with thesecorrections therein that the same may conform to the record of the casein the `Patent Office.

Signed and sealed this 22nd day of April, A. D. 1930.

. M. J. Moore, (Seal) l Acting Commissioner of Patents.

